U.S. patent number 4,154,697 [Application Number 05/868,573] was granted by the patent office on 1979-05-15 for liquid crystalline hexahydroterphenyl derivatives.
This patent grant is currently assigned to Merck Patent Gesellschaft mit beschraenkter Haftung. Invention is credited to Rudolf Eidenschink, Joachim Krause, Ludwig Pohl.
United States Patent |
4,154,697 |
Eidenschink , et
al. |
May 15, 1979 |
Liquid crystalline hexahydroterphenyl derivatives
Abstract
Novel liquid crystals have the formula ##STR1## wherein two of
the rings A, B and C are aromatic and the third is a
trans-1,4-disubstituted cyclohexane ring and R is alkyl or alkoxy
each of 1 - 12 C-atoms. These compounds are particularly useful as
additional components in liquid crystal dielectrics whereby the
clear point of the dielectric is raised and the viscosity thereof
is not deleteriously affected.
Inventors: |
Eidenschink; Rudolf (Darmstadt,
DE), Krause; Joachim (Darmstadt, DE), Pohl;
Ludwig (Darmstadt, DE) |
Assignee: |
Merck Patent Gesellschaft mit
beschraenkter Haftung (Darmstadt, DE)
|
Family
ID: |
5998795 |
Appl.
No.: |
05/868,573 |
Filed: |
January 11, 1978 |
Foreign Application Priority Data
|
|
|
|
|
Jan 15, 1977 [DE] |
|
|
2701591 |
|
Current U.S.
Class: |
252/299.63;
558/411; 558/423; 558/426; 562/469; 562/492; 562/867; 568/323;
568/329; 568/807 |
Current CPC
Class: |
C07C
1/22 (20130101); C07C 45/46 (20130101); C07C
49/792 (20130101); C09K 19/3003 (20130101); C07C
1/22 (20130101); C07C 13/28 (20130101); C07C
45/46 (20130101); C07C 49/792 (20130101); C07C
2521/18 (20130101); C07C 2523/44 (20130101); C07C
2601/14 (20170501) |
Current International
Class: |
C07C
49/792 (20060101); C07C 49/00 (20060101); C07C
1/22 (20060101); C07C 1/00 (20060101); C07C
45/00 (20060101); C07C 45/46 (20060101); C09K
19/30 (20060101); C07C 121/64 (); C07C 121/75 ();
C09K 003/34 () |
Field of
Search: |
;260/465R,465F ;252/299
;350/350 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Torrence; Dolph H.
Attorney, Agent or Firm: Millen & White
Claims
What is claimed is:
1. A hexahydroterphenyl compound of the formula ##STR18## wherein
two of the rings A, B and C are aromatic and the third is a
trans-1,4-disubstituted cyclohexane ring and R is alkyl or alkoxy
each of 1-12 C atoms.
2. The hexahydroterphenyl compound of claim 1 having the formula
##STR19##
3. The hexahydroterphenyl compound of claim 1 having the formula
##STR20##
4. The hexahydroterphenyl compound of claim 1 having the formula
##STR21##
5. The hexahydroterphenyl compound of claim 1 wherein R is an
unbranched alkyl or alkoxy.
6. The hexahydroterphenyl compound of claim 1 wherein R is alkyl of
1-10 C atoms.
7. The hexahydroterphenyl compound of claim 1 wherein R is alkoxy
of 1-8 C atoms.
8. 4-cyano-4'-(trans-4-n-propylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-butylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-pentylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-hexylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-heptylcyclohexyl)-biphenyl and
4-cyano-4'-(trans-4-n-octylcyclohexyl)-biphenyl, each a compound of
claim 1.
9. 4-cyano-4'-(trans-4-methoxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-ethoxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-propyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-butyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-pentyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-hexyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-heptyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-octyloxycyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(2-methylbutyloxy)-cyclohexyl]-biphenyl and
4-cyano-4'-[trans-4-(2-ethylhexyloxy)-cyclohexyl]-biphenyl, each a
compound of claim 1.
10. Trans-4-(4-n-propylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-butylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-pentylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-hexylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-heptylphenyl)-1-(4-cyanophenyl)-cyclohexane and
trans-4-(4-n-octylphenyl)-1-(4-cyanophenyl)-cyclohexane, each a
compound of claim 1.
11. A liquid crystalline dielectric composition having at least 2
liquid crystalline components, wherein at least one component is a
hexahydroterphenyl compound of claim 1.
12. The composition of claim 11 wherein at least one component is
not a hexahydroterphenyl compound of claim 1.
13. The liquid crystalline dielectric composition of claim 11,
wherein the amount of hexahydroterphenyl compound is up to 30
percent by weight.
14. A liquid crystalline display element whose dielectric comprises
a hexahydroterphenyl compound of claim 1.
Description
BACKGROUND OF THE INVENTION
The present invention is concerned with liquid crystalline
cyclohexane derivatives and with dielectric compositions containing
them.
To an increasing extent, the properties of nematic or
nematic-cholesteric liquid crystalline materials are being utilized
for electro-optical indicating elements. This utility derives from
the fact that the optical properties of these materials such as
light scattering, birefringence, reflecting power or color, change
under the influence of electric fields. The function of such
indicator elements thereby depends, for example, upon the
phenomenon of dynamic scattering, the deformation of aligned
phases, the Schadt-Helfrich effect in the twisted cell or the
cholestericnematic phase transition.
For the technical use of these effects in electronic elements,
liquid crystalline materials which must satisfy a plurality of
requirements are needed. Especially important is a chemical
stability to moisture, air and physical influences, such as heat,
infra-red, visible and ultra-violet radiation and direct and
alternating electric fields. Furthermore, there is required a
liquid crystalline mesophase in the temperature range of at least
+10.degree. C. to +60.degree. C. and preferably of 0.degree. C. to
60.degree. C., and a low viscosity at ambient temperature, which
should preferably be not more than 70 cP. Finally, they should not
exhibit an inherent absorption of visible light, i.e., they must be
colorless.
A number of liquid crystalline compounds is already known. These
satisfy the stability requirements demanded of dielectrics for use
in electronic display elements and are also colorless. These
include, in particular, the p,p'-disubstituted benzoic acid phenyl
esters described in U.S. Patent Specification No. 4,002,670 (German
Patent Application No. 2,139,628) and the p,p'-disubstituted
biphenyl derivatives described in U.S. Patent Specification No.
3,947,375 (German Patent Application No. 2,356,085). In both of
these classes of compounds, as well as in other known series of
compounds having a liquid crystalline mesophase, there are no
individual compounds which form a liquid crystalline nematic
mesophase in the required temperature range of 10.degree. C. to
60.degree. C. Therefore, as a rule, mixtures of two or more
compounds are produced in order to obtain materials which can be
used as liquid crystalline dielectrics.
For this purpose, it is customary to mix at least one compound
having a low melting or clear point with another having a
distinctly higher melting and clear point. A mixture is thus
normally obtained, the melting point of which is below that of the
lower melting component. However, optimal dielectrics cannot be
prepared in this way since the components with the high melting and
clear points almost always impart a high viscosity to the mixture.
Consequently, the switch times of the electro-optical indicator
elements produced therewith are thereby prolonged in an undesirable
manner.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide liquid
crystalline dielectrics which exhibit a nematic phase in the
required temperature range and permit short switch times in liquid
crystal cells at ambient temperature.
In a composition aspect, this invention relates to novel
hexahydroterphenyl derivatives of the general formula (I) ##STR2##
wherein two of the rings A,B and C are aromatic and the third is a
trans-1,4-disubstituted cyclohexane ring and R is alkyl or alkoxy
each of 1 - 12 C-atoms. In another composition aspect, this
invention provides mixtures containing the novel compounds of this
invention. These compounds and mixtures are outstandingly useful
materials for the production of liquid crystalline dielectrics.
Furthermore, the present invention provides liquid crystalline
dielectric compositions containing at least two liquid crystalline
components, at least one of which is a hexahydroterphenyl
derivative of formula (I).
This invention also provides a liquid crystal display element
wherein the dielectric comprises a compound of formula (I).
DETAILED DISCUSSION
Although the compounds of formula (I) in general possess such high
melting (over 90.degree. C.) and clear points (over 170.degree. C.)
that they individually are normally not suitable for use as
dielectrics in electronic indicator elements operated at room
temperature, addition of these compounds to other liquid
crystalline substances achieves a significant lowering of melting
point, as well as an advantageous increase in the clear point. At
the same time, they do not cause an undesired increase in viscosity
of the mixture.
The hexahydroterphenyl derivatives of formula (I) fall into three
classes:
4-(4-trans-R-cyclohexyl)-4'-cyanobiphenyls of formula (II)
##STR3##
trans-1-(p-R-phenyl)-4-(p-cyanophenyl)-cyclohexanes of formula
(III). ##STR4## and 4-R-4'-(4-trans-cyanocyclohexyl)-biphenyls of
formula (IV) ##STR5## wherein R in the formulae (II), (III) and
(IV) is as defined for formula (I).
The hexahydroterphenyl derivatives of formula (I) possess a
positive dielectric anisotropy and are, therefore, suitable for use
as components of liquid crystalline dielectrics in those indicator
elements which function on the basis of the Schadt-Helfrich effect
in the twisted nematic cell or which utilize the phenomenon of the
cholesteric-nematic phase transition.
Substituent R in the compounds of formula (I) can be
straight-chained or branched. When R is straight-chained, it can be
methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl,
n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl or the
corresponding alkoxy radicals. Such straight-chained compounds of
formula (I) generally possess especially high clear points.
Especially preferred compounds of formula (I) are those in which R
is an alkyl radical of 1- 10, especially 3- 8, or an alkoxy radical
of 1- 8, especially 3- 7, C-atoms.
Compounds of formula (I) having branched R substituents are also
included and sometimes are also of high importance since they
frequently display better solubility properties in the customary
liquid crystalline base mixtures. Such branched R substituents
preferably contain not more than one chain branching. Preferred
branched R substituents are those in which the carbon atom chain is
branched on the binding carbon atom or on one of the two next
carbon atoms. Of particular importance among these are those
branched groups in which there is in the 1-, 2- or 3-position a
methyl or ethyl group, for example, isopropyl, 1-methylpropyl,
2-methylpropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl,
1-methylpentyl, 1-ethylpentyl, 2-methylpentyl, 1-methylhexyl,
2-ethylhexyl or 1-methylheptyl, as well as the corresponding alkoxy
groups. Among these, those radicals having a main chain length of
from 4 to 6 carbon atoms are preferred.
Generally, when R is a branched chain group, from 4 to 8 total
carbon atoms are preferred.
The compounds of formula (I) are prepared in the conventional
fashion for such compounds. For example, a compound of formula (V)
##STR6## wherein R is as defined for formula (I), may be reacted
with a compound of formula (VI) ##STR7## wherein X is H or an amino
group protected against reaction with organo-metallic reagents by
protective groups which are easily split off, for example
trimethylsilyl groups, and Y is --Me.sup.1 or --Me.sup.2 --Hal,
whereby Me.sup.1 and Me.sup.2 are metal atoms of Main Groups I or
II of the Periodic Table of the Elements, preferably lithium or
magnesium, and Hal is halogen, preferably chlorine or bromine. The
resultant product is hydrolyzed to a compound of formula (VII)
##STR8##
After conventional separation of the cis-trans-isomeric alcohols
(VII), the separated isomers are individually reduced in fully
conventional manner, for example, by catalytic hydrogenation, with
inversion or retention of the configuration of the benzylpositioned
carbon atoms, to the trans-conformation hexahydroterphenyl
derivatives (VIII). ##STR9##
X in these compounds of formula (VIII), is then converted also in
fully conventional fashion into a nitrile group. Thus, for example,
when X is a hydrogen atom, the compound of formula (VIII) is
reacted in the presence of aluminium chloride with acetyl chloride
to produce the corresponding acetophenone derivative. This is then
oxidized, e.g., with hypohalite or with iodine, to the
corresponding benzoic acid (IX) ##STR10##
The benzoic acid (IX) is then converted in fully conventional
fashion into the nitrile (II) by successive treatment with thionyl
chloride, ammonia and phosphorus oxychloride, via the intermediates
of the corresponding benzoyl chloride and benzamide.
Alternatively, a compound of formula (VIII), in which X is
hydrogen, can be conventionally reacted with thallium
tristrifluoroacetate to produce the corresponding phenyl
thallium-bis-trifluoroacetate. This can then be subjected to
conventional UV irradiation in aqueous solution in the presence of
potassium cyanide, whereby the nitrile (II) is formed.
Compounds of formula (VIII), in which X is a protected amino group,
after conventional removal of the protective group, can be
converted into the nitrile (II) by diazotization and subsequent
reaction with dicyanocuprate.
The compounds of formula (III) can also be prepared fully
analogously to the compounds of formula (II) by first reacting a
4-alkyl-(or alkoxy)-phenyl magnesium bromide with
4-phenylcyclohexanone, followed by hydrolysis of the reaction
mixture, thereby obtaining the cis-trans-isomeric 1-(4-alkyl- or
alkoxyphenyl)-4-phenyl-cyclohexanols. After separation and
hydrogenation with inversion or retention of the configuration,
these are converted into trans-4-(4-alkyl- or
alkoxyphenyl)-1-phenyl-cyclohexane. The nitrile group is introduced
into the 4-position of the unsubstituted phenyl nucleus of these
compounds as described above via the corresponding acetophenone
derivative or the phenyl thallium bis-trifluoroacetate
derivative.
The compounds of formula (IV) may be obtained by reacting
cyclohexene with acetyl chloride in the presence of aluminum
chloride to produce 4-acetylcyclohexyl chloride. This, in turn, is
reacted in the presence of aluminum chloride with a compound of the
formula R-(p)--C.sub.6 H.sub.4 --C.sub.6 H.sub.5 to give
4--[4--(R)--biphenylyl--(4')]-1-acetylcyclohexane. The acetyl group
in this intermediate product is converted into a carboxyl group by
oxidation with hypohalite, and the latter group converted via the
acid chloride and acid amide into a nitrile group.
All the foregoing chemical reactions involved in the several
preparative schemes discussed above are well known and may be
conducted using the conventional conditions disclosed in the
literature, e.g., in Houben-Weyl, Methoden der Organischen Chemie
(Methods of Organic Chemistry), Fourth Edition,
Georg-Thieme-Verlag, Stuttgart, Germany.
The starting materials for the preparation of the compounds of this
invention are either known or can be readily prepared without
difficulty using processes known and described in the literature.
Thus, for example, the 4-alkylcyclohexanones (formula V, R = alkyl)
can be obtained by catalytically hydrogenating the corresponding
4-alkylphenols. The so-obtained 4-alkylcyclohexanols are then
oxidized to the corresponding ketones. The 4-alkoxycyclohexanones
can be prepared analogously by hydrogenation of the corresponding
hydroquinone hemiethers and subsequent oxidation of the so-obtained
4-alkoxycyclohexanols.
The compounds of formula (I) are valuable components for use in
liquid crystalline dielectrics suitable for the production of
electro-optical indicator elements.
The dielectrics of this invention consist of two or more
components, including at least one of formula (I). The additional
components are preferably nematic or nematogenic. Suitable classes
of such compounds include the azobenzenes, azoxybenzenes,
biphenyls, Schiff bases, especially benzylidene derivatives, phenyl
benzoates, phenyl cyclohexanes, optionally halogenated stilbenes,
diphenylacetylene derivatives, diphenyl nitrones and substituted
cinnamic acids. The most important compounds for use as such
additional components have the formula (X): ##STR11## wherein
______________________________________ A is CHCH ##STR12## CX'CH
##STR13## CHCX' ##STR14## CC ##STR15## NN ##STR16## N(O)N ##STR17##
NN(O) CHN OCO NCH COO CHN(O) SCO N(O)CH COS
______________________________________
or a C--C single bond. When A is --CO--O--, --O--CO-- or a C--C
single bond, one of the two phenyl rings can be replaced by a
trans-cyclohexyl ring. X' is halogen, preferably Cl. R.sub.1 and
R.sub.2 may be the same or different and ech is alkyl, alkoxy,
alkanoyl, alkanoyloxy or alkoxycarbonyloxy radicals of up to 18,
preferably up to 8 C-atoms. Furthermore, one of R.sub.1 and R.sub.2
can also be a cyano-, nitro or isonitrile group. In the case of
most of these compounds, R.sub.1 and R.sub.2 are preferably
different, whereby one of the radicals very usually is an alkyl or
alkoxy group. However, a large number of other variant combinations
of the permissible substituents are also conventional. Many such
nematic substances are commercially available.
The dielectrics of this invention contain up to 30, normally 1- 20,
preferably 5- 14 parts by weight, based on the total weight of the
liquid-crystalline dielectric, of one or more of the compounds of
the formula (I).
By addition of the compounds of formula (I), independent of the
nature and composition of the liquid crystalline base substance
increases of the clear point of 5- 40 degrees Centigrade are
achieved. At the same time, the viscosity of the base substance,
and thus the switch time of indicator elements using the resultant
dielectrics, is not deleteriously affected.
By inclusion of suitable additives, the liquid crystalline
dielectrics of this invention can be modified so that they can be
employed in all previously known types of indicator elements which
use liquid crystal having positive dielectric anisotropy. Such
additives are conventional and are known to the skilled artisan.
They are described in detail in the relevant literature. For
example, conventional additives exist for changing the dielectric
anisotropy and/or the orientation of the nematic phases. Substances
of this type are described, for example, in laid-open German Patent
Applications P 22 09 127, P 23 21 632 and P 26 11 453.
Without further elaboration, it is believed that one skilled in the
art can, using the preceding description, utilize the present
invention to its fullest extent. The following preferred specific
embodiments are, therefore, to be construed as merely illustrative,
and not limitative of the remainder of the disclosure in any way
whatsoever.
In the Examples, m.p. is the melting point and c.p. the clear point
of a liquid crystalline substance in degrees Celsius. Boiling
temperatures are indicated by b.p. Unless otherwise noted,
statements of parts or percentages refer to parts by weight or
percentages by weight. All viscosities are measured at
20.degree..
EXAMPLE 1
(a) To a solution of biphenyl magnesium bromide prepared from 46.6
g of 4-bromobiphenyl, and 4.9 g of magnesium turnings in 250 ml of
diethyl ether, there is added dropwise with stirring and cooling,
over the course of one hour, a solution of 34.0 g of
4-n-pentylcyclohexanone in 100 ml of diethyl ether. The reaction
mixture is further heated to the boil for 1 hour and then poured
into a solution of 20 ml of concentrated hydrochloric acid in 400
ml of ice water. The ether phase is separated off and the aqueous
phase shaken out twice with 100 ml of diethyl ether. The combined
ether phases are washed with 5% sodium hydrogen carbonate solution
and then with water, dried over sodium sulphate and evaporated. The
residue is subjected to a separation on a column filled with silica
gel. The 1-biphenylyl-cis-4-n-pentyl-r-cyclohexanol eluted with
petroleum ether (boiling range 40.degree.- 60.degree. ) is
dissolved in 500 ml of ethanol and hydrogenated in the presence of
25 g of moist Raney nickel at normal pressure for 72 hours. The
trans compound, which is eluted with a mixture of petroleum ether
(40.degree.- 60.degree.) and diethyl ether (15 volume percent), is
dissolved in 500 ml of ethanol and hydrogenated in the presence of
8 g of palladium charcoal (5% Pd) at normal pressure for 48 hours.
After filtering off the catalyst, the alcoholic solutions are
combined and evaporated. The
4-[trans-(4-n-pentyl)-cyclohexyl]-biphenyl obtained in oily form is
further worked-up without purification.
(b) A suspension of 14.6 g of aluminum chloride in 100 ml of
dichloromethane is successively mixed, with ice cooling, with 8.6 g
of acetyl chloride and a solution of 33.7 g of
4-[trans-(4-n-pentyl)-cyclohexyl] -biphenyl in 100 ml of
dichloromethane. The reaction mixture is further stirred for 2
hours, poured onto 300 g of ice and mixed with sufficient
concentrated hydrochloric acid that the precipitated aluminum
hydroxide is dissolved. The organic phase is separated off and the
aqueous phase washed twice with 100 ml amounts of dichloromethane.
The combined organic phases are dried over calcium chloride and
evaporated. The
4-acetyl-4'-[trans-(4-n-pentyl)-cyclohexyl]-biphenyl left behind is
recrystallised from ethanol; m.p. 125.degree., c.p.
200.degree..
(c) 14.0 g of 4-acetyl-4'-[trans-(4-n-pentyl)-cyclohexyl] -biphenyl
are heated, together with 30 g of iodine and 100 ml of pyridine on
a steambath for 2 hours. After the pyridine is evaporated off under
reduced pressure, the residue is dissolved in chloroform and
purified over a short silica gel column. The eluate is evaporated
and the 4'-[trans-(4-n-pentyl)-cyclohexyl]-4-biphenylcarboxylic
acid left behind is heated to the boil for 2.5 hours with 30 ml of
thionyl chloride. After distilling off the excess thionyl chloride,
the 4'-[trans-(4-n-pentyl)-cyclohexyl]-4-biphenylcarboxylic acid
chloride is dissolved in 250 ml of dioxane and this solution mixed
with 100 ml of 25% aqueous ammonia solution. The reaction mixture
is poured into 1.5 liters of ice water and the precipitated
4'-[trans-(4-n-pentyl)-cyclohexyl]-4-biphenyl-carboxylic acid amide
filtered off and dried. The dried amide is dissolved at 40.degree.
in 170 ml of dimethyl formamide. To this solution are added
dropwise at 50.degree. , in the course of 30 minutes, 26 g of
phosphorus oxide trichloride. After 1 hour, the reaction mixture is
poured into 300 ml of ice water. By several extractions with 100 ml
amounts of dichloromethane, washing of the extracts with 5% sodium
bicarbonate solution and then with water, drying over sodium
sulphate and evaporation,
4-cyano-4'-(trans-4-pentyl-cyclohexyl)-biphenyl is isolated. It is
purified by recrystallisation from ethanol; m.p. 93.degree., c.p.
219.degree..
There are prepared analogously:
4-cyano-4'-(trans-4-methylcyclohexyl)-biphenyl, m.p. 151.degree.,
c.p. 186.degree.;
4-cyano-4'-(trans-4-ethylcyclohexyl)-biphenyl.
4-cyano-4'-(trans-4-n-propylcyclohexyl)-biphenyl, m.p. 132.degree.,
c.p. 230.degree.;
4-cyano-4'-(trans-4-isopropylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-butylcyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylpropyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans- 4-(2-methylpropyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(1-methylbutyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-methylbutyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(3-methylbutyl)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-hexylcyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylpentyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-methylpentyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-n-heptylcyclohexyl)-biphenyl, m.p. 77.degree.,
c.p. 206.degree.;
4-cyano-4'-[trans-4-(1-methylhexyl)-cyclohexyl]biphenyl,
4-cyano-4'-[trans-4-(1-ethylpentyl)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-octylcyclohexyl)-biphenyl, m.p. 61.degree.,
c.p. 188.degree.;
4-cyano-4'-[trans-4-(1-methylheptyl)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-ethylhexyl)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-nonycyclohexyl)-biphenyl, m.p.
63.degree.,c.p. 192.degree.;
4-cyano-4'-(trans-4-n-decylcyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-n-undecylcyclohexyl)-biphenyl, and
4-cyano-4'-(trans-4-n-dodecylcyclohexyl)-biphenyl.
EXAMPLE 2
(a) To a solution of ethyl magnesium bromide prepared from 45.0 g
of ethyl bromide and 9.6 g of magnesium turnings in 400 ml of
diethyl ether, thee is added dropwise a solution of 49.6 g of
4-amino-4'-bromobiphenyl in 150 ml of diethyl ether. Subsequently,
there are added at room temperature 43.2 g of trimethylsilyl
chloride in 200 ml of diethyl ether. After heating under reflux for
1 hour, the solvent is evaporated off and the residue is extracted
with petroleum benzine (boiling range 60.degree.- 80.degree.). From
the extract, there are obtained by crystallisation 42.0 g of
4-N,N-bis(trimethylsilyl)-amino-4'-bromobiphenyl. This is dissolved
in 200 ml of diethyl ether and mixed at 0.degree. with 54 ml of 2
molar butyl lithium solution in hexane. After stirring for 30
minutes, a solution of 18.2 g of 4-n-butyloxycyclohexanone in 50 ml
of diethyl ether is added dropwise thereto. The mixture is heated
to the boil for 1 hour and, after cooling to room temperature,
stirred with 200 ml of 1N aqueous hydrochloric acid. The organic
phase is washed with 100 ml of 5% sodium bicarbonate solution and
then with 100 ml of water, dried with sodium sulphate and, after
removal of the solvent, analogously to Example 1(a), the residue is
separated on a silica gel column, into
1-(4-amino-4'-biphenylyl)-cis-4-n-butyloxy-r-cyclohexanol and
1-(4-amino-4'-biphenylyl)-trans-4-n-butyloxy-4-cyclohexanol. The
isomers are hydrogenated analogously to Example 1(a) in the
presence of Raney nickel or of palladium charcoal.
(b) A solution of 24 g of
4-amino-4'-(trans-4-n-butyloxycyclohexyl)-biphenyl, obtained in the
hydrogenation, in 40 ml of semi-concentrated hydrochloric acid is
slowly mixed at 0.degree., with stirring, with a solution of 5.6 g
of sodium nitrite in 35 ml of water. The diazonium salt solution
obtained is covered with 150 ml of toluene and, while stirring,
slowly mixed with 90 ml of a sodium dicyanocuprate solution
prepared from 25 g of copper sulphate pentahydrate and 21 g of
sodium cyanide in 100 ml of water. The reaction mixture is further
stirred vigorously for 30 minutes at about 80.degree..
Subsequently, the toluene phase is separated off, washed twice with
50 ml amounts of water, dried over sodium sulphate and evaporated.
The 4-cyano-4'-(trans-4-n-butyloxycyclohexyl)-biphenyl remaining
behind is recrystallised from ethanol.
There are prepared analogously:
4-cyano-4'-(trans-4-methoxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-ethoxycyclohexyl)biphenyl,
4-cyano-4'-(trans-4-n-propyloxycyclohexyl)-biphenyl,
4-cyano-4'-(trans-4-isopropyloxyclohexy)-biphenyl,
4-cyano-4'-[trans-4-(1-methylpropyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-methylpropyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-pentyloxycyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylbutyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-methylbutyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(3-methylbutyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-hexyloxycyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylpentyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-methylpentyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-heptyloxycyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylhexyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-octyloxycyclohexyl)-biphenyl,
4-cyano-4'-[trans-4-(1-methylheptyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-[trans-4-(2-ethylhexyloxy)-cyclohexyl]-biphenyl,
4-cyano-4'-(trans-4-n-nonyloxycyclohexyl)-biphenyl, and
4-cyano-4'-(trans-4-n-decyloxycyclohexyl)-biphenyl.
EXAMPLE 3
(a) To a solution of 4-n-pentylphenyl magnesium bromide prepared
from 45.5 g of 4-n-pentylbromobenzene and 4.9 g of magnesium
turnings in 250 ml of diethyl ether there is added dropwise, with
stirring and cooling, a solution of 34.8 g of 4-phenylcyclohexanone
in 100 ml of diethyl ether. The reaction mixture is further heated
to the boil for 1 hour and then poured into a solution of 20 ml of
concentrated hydrochloric acid in 400 ml of ice water. The ether
phase is separated off and the aqueous phase further shaken out
twice with 100 ml of diethyl ether. The combined ether phases are
washed with 5% sodium hydrogen carbonate solution and then with
water, dried over sodium sulphate and evaporated. The residue is
subjected to a separation via a column filled with silica gel. As
elution agents, petroleum ether (40.degree. - 60.degree.) is first
used and then petroleum ether/diethyl ether mixtures with a
proportion of diethyl ether increasing from 2 to 15 vol.%. There
are obtained about equal amounts of
1-(4-n-pentylphenyl)-cis-4-phenyl-r-cyclohexanol and
1-(4-n-pentylphenyl)-trans-4-phenyl-r-cyclohexanol in oily form.
The cis compound is dissolved in 500 ml of ethanol and hydrogenated
in the presence of 25 g of moist Raney nickel at normal pressure
for 72 hours. The trans compound is dissolved in 500 ml of ethanol
and also hydrogenated for 48 hours in the presence of 8 g of
palladium charcoal (5% Pd). After the filtering off of the
catalysts, the alcoholic solutions are combined and evaporated. The
trans-4 -(4-n-pentylphenyl)-1-phenyl-cyclohexane obtained in oily
form is further worked-up without purification.
(b) A suspension of 14.6 g of aluminium chloride in 100 ml of
dichloromethane is successively mixed, with ice cooling, with 8.6 g
of acetyl chloride and a solution of 33.7 g of
trans-(4-(4-n-pentylphenyl)-1-phenylcyclohexane in 100 ml of
dichloromethane. The reaction mixture is further stirred for 2
hours, poured onto 300 g of ice and mixed with sufficient
concentrated hydrochloric acid that the precipitated aluminum
hydroxide is dissolved. The organic phase is separated off and the
aqueous phase washed twice with 100 ml amounts of dichloromethane.
The combined organic phases are dried over calcium chloride and
evaporated. The
trans-4-(4-n-pentylphenyl)-1-(4-acetylphenyl)-cyclohexane remaining
behind is recrystallised from ethanol.
(c) 14.0 g of
trans-4-(4-n-pentylphenyl)-1-(4-acetylphenyl)-cyclohexane are
heated for 2 hours on a steambath, together with 30 g of iodine and
100 ml of pyridine. After the evaporation of the pyridine under
reduced pressure, the residue is dissolved in chloroform and
purified over a short silica gel column. The eluate is evaporated
and the 4-[trans-4-(4-n-pentylphenyl)-cyclohexyl]-benzoic acid
remaining behind is brought to the boil for 2.5 hours with 30 ml of
thionyl chloride. After distilling off the excess thionyl chloride,
the 4-[trans-4-(4-n-pentylphenyl)-cyclohexyl]-benzoyl chloride is
dissolved in 250 ml of dioxane and this solution mixed with 100 ml
of 25% aqueous ammonia solution. The reaction mixture is poured
into 1.5 liters of ice water and the precipitated
4-[trans-4-(4-n-pentylphenyl)-cyclohexyl]-benzamide filtered off
and dried. The dry amide is dissolved at 40.degree. in 170 ml of
dimethyl formamide. To this solution are added dropwise at
50.degree. , in the course of 30 minutes, 26 g of phosphorus oxide
trichloride. After 1 hour the reaction mixture is poured into 300
ml of icewater. After extracting several times with 100 ml amounts
of dichloromethane, washing of the extracts with 5% sodium
bicarbonate solution and then with water, drying over sodium
sulphate and evaporation, there is obtained
trans-4-(4-n-pentylphenyl)-1-(4-cyanophenyl)-cyclohexane which is
purified by recrystallisation from ethanol; m.p. 80.degree., c.p.
160.degree..
There are obtained analogously:
trans-4-(4-methylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-ethylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-propylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-isopropylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-butylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylpropyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[2-(2-methylpropyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylbutyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-methylbutyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(3-methylbutyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-hexylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylpentyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-methylpentyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-heptylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylhexyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-octylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylheptyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-ethylhexyl)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-nonylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-decylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-undecylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-dodecylphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-methoxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-ethoxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-propyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-isopropyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-butyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylpropyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-methylpropyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-pentyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylbutyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-methylbutyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(3-methylbutyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-hexyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylpentyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-methylpentyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-heptyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylhexyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-octyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(1-methylheptyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-[4-(2-ethylhexyloxy)-phenyl]-1-(4-cyanophenyl)-cyclohexane,
trans-4-(4-n-nonyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane, and
trans-4-(4-n-decyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane.
EXAMPLE 4
(a) To a suspension of 66.6 g of anhydrous aluminum chloride in 200
ml of carbon disulphide there are added at -15.degree., with
stirring, 39 g of acetyl chloride and thereafter 41 g of
cyclohexene. The reaction mixture is stirred for 30 minutes at
-15.degree. and then the upper carbon disulphide layer is removed
and replaced by 400 ml of a solution of 105 g of 4-n-butylbiphenyl
in carbon disulphide. After the addition of a further 33.3 g of
aluminum chloride, it is warmed, with stirring, to room temperature
and further stirred until the end of the HCl evolution. Thereafter,
it is poured onto water, the separated aluminum hydroxide is
brought into solution with hydrochloric acid, and the organic phase
is separated off, dried and distilled. After the stripping off of
the solvent, there remains
4-acetyl-1-[4'-n-butylbiphenylyl-(4)]-cyclohexane as yellowish,
wax-like product; yield 64 g.
(b) Analogously to Example 1 (c), from 50 g of
4-acetyl-1-['-n-butylbiphenylyl-(4)]-cyclohexane, there are
obtained, by successive reaction with iodine/pyridine, thionyl
chloride, ammonia solution and phosphorus oxide trichloride, 21,8 g
of 4-cyano-1-[4'-n-butylbiphenylyl-(4)]-cyclohexane.
There are prepared analogously:
4-cyano-1-[4'-methylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-ethylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-propylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-pentylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-hexylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-heptylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-octylbiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-methoxybiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-ethoxybiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-propyloxybiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-butyloxybiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-pentyloxybiphenylyl-(4)]-cyclohexane,
4-cyano-1-[4'-n-hexyloxybiphenylyl-(4)]-cyclohexane, and
4-cyano-1-[4'-n-heptyloxybiphenylyl-(4)]-cyclohexane.
The following Examples concern the liquid crystalline dielectrics
of this invention:
EXAMPLE 5
A mixture of 41% trans-4-(4-cyanophenyl)-1-n-propylcyclohexane, 35%
trans-4-(4-cyanophenyl)-1-n-pentyl-cyclohexane and 24%
trans-4-(4-cyanophenyl)-1-n-heptylcyclohexane (prepared analogously
to Example 1 from phenyl megnesium bromide and the corresponding
4-n-alkyl-cyclohexanones) has a clear point of 52.degree. and a
viscosity of 21 cP at 20.degree.. After the addition of 12%
(referred to the weight of the base mixture) of
4-cyano-4'-(trans-4-n-pentyl-cyclohexyl)-biphenyl, the dielectric
has a clear point of 72.degree. and a viscosity of 29 cP.
EXAMPLE 6
A mixture of 37% of 4-n-pentyl-4'-cyanobiphenyl, 43%
4-n-heptyl-4'-cyanobiphenyl, as well as 10% each of
4-n-pentyloxy-4'-cyanobiphenyl and 4-n-heptyloxy-4'-cyano-biphenyl,
has a clear point of 45.degree. (35 cP). By the addition of 18%
(referred to the weight of the base mixture) of
trans-4-(4-n-pentylphenyl)-1-(4-cyanophenyl)-cyclohexane, the clear
point increases to 66.degree., whereas the viscosity remains
practically unchanged (37 cP).
EXAMPLE 7
A mixture of 67% anisic acid 4-n-pentylphenyl ester and 33%
4-n-hexyloxybenzoic acid 4'-n-pentylphenyl ester has a clear point
of 49.degree. and a viscosity of 59 cP. By the addition of 21.5%
4-cyano-4'-(trans-4-n-heptylcyclohexyl)-biphenyl, a mixture is
obtained which possesses a clear point of 83.degree. and a
viscosity of 50 cP.
EXAMPLE 8
A mixture of 40% 4-n-butyl-4'-methoxyazoxybenzene, 22%
4-ethyl-4'-methoxyazoxybenzene, 20% dimethylaminobenzonitrile and
18% 4-(4-n-butylbenzoyloxy)-benzoic acid 4'-n-butylphenyl ester has
a clear point of 31.degree. and a viscosity of 50 cP. By the
addition of 15%
trans-4-(4-n-hexyloxyphenyl)-1-(4-cyanophenyl)-cyclohexane, the
clear point increases to 57.degree., whereas the viscosity
decreased to 45 cP.
The preceding examples can be repeated with similar success by
substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
From the foregoing description, one skilled in the art can easily
ascertain the essential characteristics of this invention, and
without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *